Compliance voltage in an implantable stimulator governs a maximum level of stimulation current that can be delivered by the implantable stimulator via one or more electrodes to one or more stimulation sites within a patient. A compliance voltage that is higher than absolutely necessary to generate and deliver a desired stimulation current causes the implantable stimulator to operate in an inefficient manner. For example, the excess compliance voltage contributes to power loss that results in a reduced battery life of the implantable stimulator. On the other hand, a compliance voltage less than that which is needed to generate and deliver a desired stimulation current inhibits optimal stimulation performance by the implantable stimulator. For example, a sub-optimal compliance voltage limits the maximum stimulation rate at which the implantable stimulator may apply stimulation current to the one or more stimulation sites, causes undesirable stimulation artifacts, and diminishes an overall experience of the patient with the implantable stimulator.
Hence, it is desirable to maintain a compliance voltage at which an implantable stimulator operates at an optimal level. Unfortunately, maximum stimulation current level requirements vary significantly from situation to situation and from patient to patient, thereby resulting in corresponding variations in the optimal compliance voltage for these patients. For example, maximum stimulation current level requirements for a cochlear implant patient may vary depending on the particular listening environment in which the patient is situated, changes in electrode impedance, and changes in relative positioning of a cochlear stimulator implanted in the patient and its corresponding externally located sound processor. Because of such variations in maximum stimulation current level requirements, maintaining a fixed compliance voltage that is high enough to always account for a worst-case scenario is wasteful.